1. Field of the Invention
The present invention relates to an improvement in a current temperature sensitive type overload protective device to be mounted on a motor for a hermetic motor-driven compressor and an improvement in a method of attaching the same.
2. Description of the Related Art
There has been known a current/temperature sensitive type overload protective device (hereinafter, referred to a protective device) which is provided in the casing of a hermetic motor-driven compressor so as to electrically disconnect a motor for the compressor from a power source by sensing predetermined temperature values of the motor and a refrigerant gas as well as a predetermined value of overcurrent in a case that the hermetic motor-driven compressor is operated under a condition of overload.
FIGS. 5 to 10 show examples of attaching a conventional protective device to a typical hermetic motor-driven compressor as disclosed in, for instance, Japanese Unexamined Utility Model Publication 175581/1981. A protective device 5 is placed in contact with the surface of a motor end coil 3 and is fixed thereto by means of a binding string 4.
FIGS. 5, 6 and 8 show the examples that the protective device 5 is attached to the upper end portion of the motor end coil 3, and FIGS. 9 and 10 show the examples that the protective device 5 is attached to a side area of the motor end coil 3.
FIG. 7 is an enlarged perspective view showing a conventional protective device 5 wherein the main body of the protective device 5 which is an electrically charged portion is covered by an insulating layer 6 of a hard film material such as polyester film. As shown in FIG. 5, the insulating layer 6 of a polyester film is wrapped around the protective device 5 in a cylindrical form with both ends being opened wherein overlapping portions are bonded. The length l.sub.1 in the axial direction of the cylindrically formed insulating layer 6 is generally 1.5 -2 times as long as the length l.sub.0 of the protective device 5 in order to keep a sufficient distance of the space for electric insulation.
Since the insulating layer 6 is hardly deformed when it is attached to the motor end coil 3, the dimension of l.sub.1 is necessary.
Since hermetic motor-driven compressors are generally of a small size, it was difficult to attach a protective
Further, there was a problem that since the protective device 5 was placed near a portion where an upper casing 1 and a lower casing 2 were welded together to form a hermetic casing, a polyester film used generally as an insulating layer 6 for the protective device 5 was easily molten by heat of radiation at the time of welding to thereby lose the function of insulation.